How several mods share the sky

Things to know

When more than one mod sets the same property, the newest mod wins. When that mod clears its values, the one before it applies. When no mod has the property, the game’s own value comes back. The framework writes one warning to the log that names both mods when two of them set the same property.
Set and Clear work while a save is loading. They are not held back, so setting your values again from Events.SceneLoaded works. (neither is gated on SaveData.Busy.)
Nothing is ever written to the save.

Your values do not stay when a save loads or the level changes. Set them again from Events.SceneLoaded or Events.Loaded. (overrides are cleared when the game starts to load a save and on a LoadSceneMode.Single scene load. Fog and ambient values belong to the scene, so on a scene change they are not written back. A skybox material is written back.)